A conventional alternating current (AC) motor driving apparatus has a converter circuit for converting alternating current (AC) into direct current (DC), and an inverter circuit for converting DC into AC. The converter circuit includes a rectifying section for rectifying an AC voltage and a smoothing section (for example, a DC link capacitor) for smoothing a DC voltage rectified by the rectifying section.
In order to diagnose a fault of the smoothing section of the converter circuit, a diagnostic method using an output of an inverter circuit has been considered as in Patent Document 1.
However, in the diagnostic method, when another part of the converter circuit has a fault, a fault diagnosis may be wrongly occur due to failure to obtain a normal output from the inverter circuit.